The present invention relates to color liquid crystal displays and display method thereof, more particularly, to color liquid crystal displays capable of reproducing a color picture to be displayed on a color liquid crystal display element by providing read-out data from a graphic RAM, in which write data provided from a host CPU or the like is written in correspondence to the color picture, to the color liquid crystal display element.
Color liquid crystal displays are very thin and small size and light in weight and consume very low power compared to color displays using cathod-ray tubes. These displays thus find extensive applications to battery-driven portable devices such as note type personal computers, portable data terminal units and DVD players. The displays find applications not only to battery-driven portable devices but also to installation type large screen displays and monitors. Up to date, this type of displays are in a trend of increasing screen size and reducing price more vigorously than the current cathod-ray tube displays.
Such color liquid crystal displays are different in various aspects from the monochromatic, i.e., white-and-black, liquid crystal displays. In the aspect of the data quantities dealt with by this type of displays, different colors are produced in an optical color addition method using three primary, i.e., red, green and blue, color filters. That is, unlike the monochromatic liquid crystal displays, data quantities of three different colors are dealt with.
Also, the colors which are obtainable by merely combining the three primary colors are only eight in number, which is insufficient for producing a sufficient number of different colors by the optical color addition method. Therefore, the colors which can be displayed should be increased in number by providing gradations in each color. This means the necessity of greater data quantities. For example, 6-bit data is necessary for displaying 64 different colors, and 9-bit data for displaying 512 different colors. At any rate, greater data quantities are necessary compared to the monochromatic binary case of display with one-bit data.
In the meantime, if too long time is taken for reproducing a display picture, it is impossible to reproduce television pictures or like motion pictures, and the commercial value is spoiled. For this reason, in an electronic apparatus using a color liquid crystal display, the display control circuit is required to have fast operation performance compared to an electronic apparatus using a white-and-black (or monochromatic) liquid crystal display. In addition, the fast operation dictates more burdens in view of the power consumption.
In battery-driven personal computers or like electronic devices, more importance is attached to the low power consumption than in electronic devices based on the preamble of operation with AC current of a commercial power supply or the like in home or offices. For this reason, the capacity of various circuits used for the display control and liquid crystal drive is somewhat sacrificed.
Also, most display devices for color liquid crystal display employ elements which are like or similar to the conventional monochromatic liquid crystal display from the consideration of the power consumption reduction.
However, with recent pronounced infra development, environments are becoming more and more adopted to multiple media utilization, and needs of such electronic devices and portable data terminals capable of dealing with color images are increasing. The color liquid crystal displays in such electronic devices should be produced by attaching importance to the power consumption reduction.
The prior art color liquid crystal display as described above is constructed such that it can reproduce a color picture to be displayed on a color liquid crystal display element by providing read-out data from a graphic RAM, in which write data provided from a host CPU or the like is written in correspondence to the color picture, to the color liquid crystal display element. This means that the write data and the read-out data are in one-to-one correspondence relation to each other.
The write data written in the graphic RAM represent different colors and color gradations of individual display pixels, and these data are read out from the graphic RAM and provided to the color liquid crystal display element for reproducing the display color picture thereon.
Therefore, although such a color liquid crystal display gives rise to no problem in case where the individual pixels of the color picture to be displayed have very large numbers of different colors and color gradations as in a color photograph, its function is deemed to be excessive in case where the color picture to be displayed represents worked-out color contents or the like.
Worked-out color contents have only several different colors and also have fewer color gradations. Besides, in this case very large numbers of pixels of the same colors are present. Therefore, writing the same write data in the graphic RAM for each of these pixels leads to extremely great data redundancy.
Since the quantity of the write data written in the graphic RAM and the quantity of the read-out data provided to the color liquid crystal display are substantially the same irrespective of whether the color picture to be displayed have very large numbers of different colors and color gradations as in color photographs or have only several different colors and fewer color gradation as in worked-out color contents, data quantities comparable to the case where very large numbers of different colors and color gradations are present are dealt with in the case of less data quantities as in the display of worked-out color contents, it is impossible to increase the rate of data processing.
An object of the present invention, therefore, is to provide a color liquid crystal display and display method thereof capable of satisfactorily reproducing a color picture to be displayed when the color picture has very large numbers of different colors and color gradations as in color photographs while also permitting the increase of the rate of data processing when the color picture has fewer different colors and color gradations as in worked-out color contents to alleviate the data processing burdens on the host CPU or the like.
According to an aspect of the present invention, there is provided a color liquid crystal display for reproducing color picture to be displayed on a color liquid crystal display element by providing read-out data from graphic RAM, in which write data provided from a host CPU or the like in correspondence to the color picture has been written, to the color liquid crystal display element, wherein provided is control means capable of selecting a normal write mode, in which pixel data corresponding to a plurality of pixels in the write data are generated such that they each correspond to data of each pixel in the graphic RAM, and a monochromatic write mode, in which pixel data corresponding to the plurality of pixels in the write data are generated such that they can be developed to the data of the plurality of pixels in the graphic RAM.
The control means includes a monochromatic write data register for storing the pixel data corresponding to the plurality of pixels in the write data when the monochromatic write mode is selected and/or a write mode register for storing the pixel data corresponding to the plurality of pixels in the write data when the normal write mode is selected.
The monochromatic write data register stores monochromatic data corresponding to a background color of the color picture to be displayed and other color data than the background color data. The monochromatic write data register stores monochromatic data constituted by color kind data corresponding to a background color of the color picture to be displayed and sequential address data for display according to the color kind data and other color data than the background color data when the monochromatic write mode is selected. The monochromatic write data register stores monochromatic data constituted by color kind data preset for a background color of the color picture to be displayed and sequential address data for display according to the color kind data and other color data than the background color data when the monochromatic write mode is selected.
The control means includes a monochromatic write data register for storing the pixel data corresponding to the plurality of pixels in the write data when the monochromatic write mode is selected, and a write mode register for storing the pixel data corresponding to the plurality of pixels in the write data when the normal write mode is selected, the outputs of the monochromatic write data register and the write mode register being selectively taken out.
The control means does not include the write mode register but includes the monochromatic write data register in the case of a preamble that write data provided from the host CPU or the like in correspondence to the color picture to be displayed is constituted by a small number of different colors.
According to another aspect of the present invention, there is provided display method of a color liquid crystal display for reproducing color picture to be displayed on a color liquid crystal display element by providing read-out data from a memory, in which write data in correspondence to the color picture has been written, to the color liquid crystal display element, wherein a normal write mode, in which pixel data corresponding to a plurality of pixels in the write data are generated such that they each correspond to data of each pixel in the memory, and a monochromatic write mode, in which pixel data corresponding to the plurality of pixels in the write data are generated such that they can be developed to the data of the plurality of pixels in the memory is selected.
The the pixel data corresponding to the plurality of pixels in the write data under the monochromatic write mode is stored in a monochromatic write data register and the pixel data corresponding to the plurality of pixels in the write data under the normal write mode is stored in a write mode register.
Monochromatic data corresponding to a background color of the color picture to be displayed and other color data than the background color data are stored in the monochromatic write data register.
Monochromatic data constituted by color kind data corresponding to a background color of the color picture to be displayed and sequential address data for display according to the color kind data and other color data than the background color data when the monochromatic write mode are stored in the monochromatic write data register.
Monochromatic data constituted by color kind data preset for a background color of the color picture to be displayed and sequential address data for display according to the color kind data and other color data than the background color data when the monochromatic write mode are stored in the monochromatic write data register.
Output of a monochromatic write data register which stores the pixel data corresponding to the plurality of pixels in the write data under the monochromatic write mode, or a write mode register which stores the pixel data corresponding to the plurality of pixels in the write data under the normal write mode is selected.
Other objects and features will be clarified from the following description with reference to attached drawings.